Signal analysis in time and frequency

ABSTRACT

An arrangement for signal analysis provides at least one central data-processing unit and a screen unit connected to the at least one central data-processing unit, wherein the central data-processing unit calculates a spectrum and a spectrogram from a digitized signal. The at least one central data-processing unit is embodied in such a manner that it controls the screen unit in such a manner that the spectrogram of the digitized signal, the characteristic of the spectrum of the digitized signal and the characteristic of the digitized signal present in the time domain can be displayed together on the screen unit.

The invention relates to a device and a method for the analysis ofvarious signals in the time domain and also in the frequency domain.

In the development of communications systems, for example, wirelesscommunications systems, it is important that these operate in accordancewith specified standards. It is also desirable to be able to analyse thehigh-frequency communications signal generated by the mobilecommunications system in order to determine errors in the developmentprocess as quickly as possible. Any deviations in the high-frequencycommunications signal from the underlying standard can be determined inthis manner. To analyse such a high-frequency communications signal, thesignal must first be recorded digitally by means of a signal analyser,for example, an oscilloscope.

A signal analyser and a method for the latter for the analysis of arecorded high-frequency communications signal are known from EP 2 113777 A1. The high-frequency communications signal is transformed into thefrequency domain in order to display its spectrum and its spectrogram ina diagram. The disadvantage with EP 2 113 777 A1 is that not all errorsare identifiable in the spectrogram and the characteristic of thespectrum.

Accordingly, the object of the arrangement according to the inventionfor signal analysis and the method according to the invention foroperating the arrangement for signal analysis is to provide a solutionin order to condition a recorded high-frequency communications signal insuch a manner that any errors in the high-frequency communicationssignal which suggest an incorrect implementation of the underlyingstandard or defective hardware, are recognised with as high aprobability as possible.

The object is achieved with regard to the arrangement for signalanalysis by the features of some claims and with regard to the methodfor operating the arrangement for signal analysis by the features ofother claims. The present disclosure specifies a computer program withprogram-code means in order to implement all of the method steps whenthe program is executed on a computer or a digital-signal processor. Thepresent disclosure also specifies a computer-software product especiallywith program code means stored on a machine-readable carrier in order toimplement all of the method steps when the program is executed on acomputer or a digital-signal processor. Advantageous furtherdevelopments of the arrangement according to the invention for signalanalysis and the method according to the invention for operating thearrangement for signal analysis are specified in the respectivedependent claims.

The arrangement according to the invention for signal analysis providesat least one central data-processing unit and a screen unit connected tothe at least one central data-processing unit. The centraldata-processing unit calculates a spectrum and a spectrogram from adigitised signal. In this context, the at least one centraldata-processing unit is embodied in such a manner that it controls thescreen unit in such a manner that the spectrogram of the digitisedsignal, the characteristic of the spectrum of the digitised signal andthe characteristic of the digitised signal present in the time domaincan be displayed together on the screen unit. It is particularlyadvantageous that the information contained in the digitised signal canbe displayed in different ways, as completely as possible and together.As a result of the fact that the digitised signal can be displayed inthree different ways, interference can be determined particularly well.

The method according to the invention for operating the arrangement forsignal analysis, which provides a central data-processing unit and ascreen unit connected to the at least one central data-processing unit,comprises several method steps. In a first method step, the spectrum andthe spectrogram are calculated from the digitised signal by the centraldata-processing unit. In a further method step, the spectrogram of thedigitised signal, the characteristic of the spectrum of the digitisedsignal and the characteristic of the digitised signal present in thetime domain are displayed together on the screen unit by the at leastone central data-processing unit. It is particularly advantageous thatboth the spectrogram and also the characteristics of the digitisedsignal in the time domain and in the frequency domain are displayedtogether on the screen unit, which considerably facilitates the analysisof the digitised signal.

A further advantage of the arrangement according to the invention forsignal analysis is achieved if the digitised signal can be buffered bythe at least one central data-processing unit in a buffer unit and ifthe digitised signal is transformed by the at least one centraldata-processing unit into the frequency domain and can be buffered inthe buffer unit. This ensures, for example, that calculation-intensivesteps, such as the transformation of the digitised signal into thefrequency domain, only need to be implemented once.

A further advantage is achieved with the arrangement according to theinvention for signal analysis if a frequency range and time range withinthe spectrogram can be freely selected and if the characteristic of thespectrum and the time characteristic of the digitised signal can beupdated and displayed on the screen unit by the at least one centraldata-processing unit for the selected frequency range and time range,and/or if the frequency range selected in the spectrogram can be plottedby the at least one central data-processing unit in the second diagram,and/or if the time range selected in the spectrogram can be plotted bythe at least one central data-processing unit in the third diagram. Itis possible to analyse the digitised signal in greater detail in aparticularly advantageous manner as a result of the possibility that agiven frequency range and time range can be selected within thespectrogram, whereas the characteristic of the spectrum and the timecharacteristic of the digitised signal can be updated dependent upon theselected frequency range and time range. It is also particularlyadvantageous that the selected frequency range can be plotted in thecharacteristic of the spectrum and the selected time range can beplotted in the time characteristic of the digitised signal. Thisfacilitates the allocation of the individual signal components of thedigitised signal in the spectrogram to the characteristics in thefrequency and time domain.

Moreover, an advantage is achieved with the arrangement according to theinvention for signal analysis if the digitised signal present in thetime domain can be filtered through a bandpass filter, whereas the passrange of the bandpass filter corresponds to the selected frequency rangeof the first diagram for the spectrogram or to the selected frequencyrange of the second diagram for the characteristic of the spectrum.Accordingly, it can be ensured that only those signal components in thecharacteristic of the time range of the present digitised signal whichare disposed within the desired frequency range appear in the thirddiagram.

Finally, an advantage is achieved with the arrangement according to theinvention for signal analysis if the part of the digitised signal whichis disposed in the selected time range and/or frequency range can betransferred by the at least one central data-processing unit to aselection unit. Such a selection unit can evaluate, for example, thepart of the digitised signal which contains the payload data to betransmitted with regard to whether this part corresponds to thestructure of the underlying standard. The evaluation unit can alsocontain a modulation analysis.

A further advantage of the method according to the invention foroperating an arrangement for signal analysis is achieved if an arbitraryfrequency range within the second diagram for the characteristic of thespectrum can be selected, and if the time characteristic of thedigitised signal can be updated by the at least one centraldata-processing unit dependent upon the selected frequency range, and/orif the selected frequency range is plotted by the at least one centraldata-processing unit into the first diagram for the spectrogram. Thismeans that the interesting ranges within the characteristic of thespectrum can also be highlighted in the spectrogram and in the timecharacteristic for the digitised signal.

Furthermore, an advantage is achieved with the method according to theinvention for operating the arrangement for signal analysis if a timerange within the third diagram is freely selected for the timecharacteristic of the digitised signal, and if the characteristic of thespectrum is updated dependent upon the selected time range, and/or ifthe selected time range is plotted in the diagram for the spectrogram bythe at least one central data-processing unit. This means that theinteresting parts of the digitised signal which are selected in the timecharacteristic of the digitised signal can also be displayed moreclearly in the other two diagrams.

Finally, an advantage is achieved with the method according to theinvention for operating the arrangement for signal analysis if thefiltered, digitised signal is decimated in its resolution by the firstdetector unit, so that the decimated, digitised signal corresponds to aresolution of the screen unit, whereas either the mean value or meansquared value or the maximum value or the minimum value or the auto-peakvalue (German: automatischer Spitzenwert) of at least two values of thedigitised signal is calculated by the first detector unit, and/or if thedigitised signal transformed into the frequency range is decimated bythe second detector unit in its resolution, so that the decimated,digitised signal corresponds to a resolution of the screen unit, whereaseither the mean value for the mean squared value or the maximum value orthe minimum value or the auto-peak value of at least two values of thedigitised signal is calculated by the second detector unit. The variouspossibilities, with which the first and the second detector unit can beoperated, mean that even interference spurs of very short duration canbe displayed on the screen unit.

Various exemplary embodiments of the invention are described by way ofexample below with reference to the drawings. Identical subject mattersprovide the same reference numbers. In detail, the corresponding figuresof the drawings are as follows:

FIG. 1 an exemplary embodiment of a block-circuit diagram, which showsthe structure of the arrangement according to the invention for signalanalysis;

FIG. 2 a further exemplary embodiment of a block-circuit diagram of theinvention, which describes in greater detail the method of functioningof the central data-processing unit within the arrangement for signalanalysis;

FIG. 3 an exemplary embodiment, which describes in greater detail themethod of functioning of the arrangement according to the invention forsignal analysis after the loading of a signal to be analysed;

FIG. 4 a further exemplary embodiment, which describes in greater detailthe method of functioning of the arrangement according to the inventionfor signal analysis after the loading of a signal to be analysed;

FIG. 5A an exemplary embodiment, which describes in greater detail themethod of functioning of the arrangement according to the invention forsignal analysis for analysing interference within a loaded signal;

FIG. 5B a further exemplary embodiment, which describes in greaterdetail the method of functioning of the arrangement according to theinvention for signal analysis for analysing interference within a loadedsignal;

FIG. 6 an exemplary embodiment of a flow chart, which describes ingreater detail the method of functioning of the arrangement according tothe invention for signal analysis; and

FIG. 7 a further exemplary embodiment of a flow chart, which describesin greater detail the method of functioning of the arrangement accordingto the invention for signal analysis.

FIG. 1 shows an exemplary embodiment of a block-circuit diagram whichillustrates the structure of the arrangement 1 according to theinvention for signal analysis. In this context, the arrangement 1 forsignal analysis comprises at least one central data-processing unit 2.The at least one central data-processing unit 2 can comprise one or moreprocessors and/or FGPAs (English: field programmable gate array; German:im (Anwendungs-) Feld-programmierbare (Logik-) Gatter-Anordnung) and/orDPSs (English: digital signal processor; German: digitalerSignalprozessor). At least one buffer unit 3, a screen unit 4, an inputunit 5 and an evaluation unit 6 are connected to the at least onecentral data-processing unit 2.

The at least one buffer unit 3 can be, for example, a random accessmemory and/or a hard-disk memory, which is embodied within thearrangement 1 for signal analysis and/or connected to the arrangement 1for signal analysis, for example, via a network port.

The screen unit 4 is preferably a screen unit 4 with a touch-sensitivescreen. In this context, touch-sensitive screens which provide aresistive or capacitive or inductive touchscreen are used by preference.

The input unit 5 comprises all of the buttons and/or keys and otherinput elements, such as a keyboard or mouse connected to the arrangement1 for signal analysis. All of the inputs registered by the input unit 5are routed to the at least one central data-processing unit 2.

As will be explained in greater detail later, the evaluation unit 6connected to the at least one central data-processing unit 2 receivesselected components of the digitised signal 7 ₁, 7 ₂ for furtherprocessing. The evaluation unit 6 can be, for example, GSM measurementunits (English: global system for mobile communication; German:weltweites System zur mobilen Kommunikation) or UMTS measurement units(English: universal mobile telecommunications system; German:universelles mobile telekommunikationssystem). Such an evaluation unit 6can also comprise a modulation analysis.

A measured digitised signal 7 ₁, 7 ₂ is transferred to the arrangement 1for signal analysis. Such a digitised signal 7 ₁, 7 ₂ can be recorded,for example, with a signal analyser 8 or an oscilloscope. FIG. 1illustrates a simplified block-circuit diagram of a signal analyser 8for this purpose. A high-frequency communications signal 9 to beanalysed is amplified in its amplitude by an amplifier 10. Followingthis, the amplified high-frequency communications signal 9 is mixed downto an intermediate frequency 12 via a mixer 11 by means of the localoscillator signal. The high-frequency communications signal 9 mixed downto an intermediate frequency 12 is then filtered through a bandpassfilter 13, before being digitised by an analog/digital converter 14. Viaa digital down converter 15 (English: digital down converter), thedigitised high-frequency signal is mixed down into the baseband,whereas, in the illustrated exemplary embodiment, the digital downconverter 15 outputs an in-phase (German: gleichphasig) component 7 ₁and a quadrature component 7 ₂ of the digitised signal 7. The in-phasecomponent 7 ₁ and the quadrature component 7 ₂ of the digitised signal 7of the signal analyser 8 is transferred to the at least one centraldata-processing unit 2 of the arrangement 1 for signal analysis.

FIG. 1 does not show a trigger signal (German: Auslösesignal), which issupplied to the analog/digital converter 14, so that only those parts ofthe high-frequency communications signal 9 in which the triggercondition is fulfilled are digitised.

FIG. 2 shows a further exemplary embodiment of a block-circuit diagramof the invention, which describes in greater detail the method offunctioning of the central data-processing unit 2 within the arrangement1 for signal analysis. At the start, the digitised signal 7 istransferred to the at least one central data-processing unit 2 withinthe arrangement 1 for signal analysis. The digitised signal 7 isbuffered by the at least one central data-processing unit 2 in a bufferunit 3.

The digitised signal 7 is then filtered through a bandpass filter 20.The pass range of the bandpass filter 20 in this context is adjustable,as will be explained in greater detail below. The filtered, digitisedsignal 7 can then be transferred by the at least one centraldata-processing unit 2 to an evaluation unit 6.

The filtered, digitised signal 7 is also further transferred to a firstdetector unit 21. In the first detector unit 21, the filtered, digitisedsignal 7 is decimated in its resolution, so that the decimated,filtered, digitised signal 7 corresponds to a resolution of the screenunit 4. The first detector unit 21 calculates from at least two valuesof the filtered, digitised signal 7 either the mean value or the meansquared value or the maximum value or the auto-peak value. If the screenunit 4 provides, for example, a horizontal resolution of 1000 points,and if the filtered, digitised signal 7 contains, for example, 10,000measured points, the first detector unit 21 calculates from tensuccessive measured values of the filtered, digitised signal 7 the meanvalue or the mean squared value or the maximum value or the minimumvalue or the auto-peak value.

The term auto-peak value is understood to mean that the maximum valueand also the minimum value of an interval, in this case of ten measuredvalues, are taken into consideration. If, as in the above example, tenmeasured values are combined, and the largest of these ten valuesprovides the value 50, and the smallest of these ten values provides thevalue 10, the measured value 50 and also the measured value 10 areplotted at the corresponding vertical line of the screen unit 4 andoptionally connected to one another by a line. The manner in which thefirst detector unit 21 should operate can be adjusted as required via aninput unit 5. This ensures that even extremely small interference spurswithin the filtered, digitised signal 7 can be detected and shown on thedisplay.

Moreover, the digitised signal 7, which is buffered by the at least onedata-processing unit 2 in the buffer unit 3, is transformed into thefrequency domain. This is preferably implemented by means of a FastFourier Transform (German: schnelle Fourier Transformation) in the FFTblock 22. This Fourier transform is preferably implemented onco-processors specially designed for this purpose, which can beembodied, for example, within a digital-signal processor. In order totransform the entire digitised signal 7 into the frequency domain,several Fourier transformations are generally required. The digitisedsignal 7 transformed into the frequency domain is preferably buffered ina matrix 23. The columns of this matrix 23 preferably represent thefrequency range, whereas the rows of the matrix 23 represent the timerange. The matrix 23 accordingly forms the spectrogram 30 for thedigitised signal 7 transformed into the frequency domain. The manner inwhich the results of the individual Fourier transformations can becombined to form this matrix 23 can be implemented, for example, usingthe Welsh method (Welsh-periodogram).

This spectrogram is buffered by the at least one central data-processingunit 2 in the buffer unit 3. Furthermore, as will be explained below,the spectrogram can be transferred to the evaluation unit 6 in itsentirety or in parts.

Moreover, the spectrogram of the digitised signal 7 buffered in thematrix 23 can be transferred to a second detector unit 24. The seconddetector unit 24 decimates the digitised signal 7 transformed into thefrequency domain in its resolution in such a manner that the decimated,digitised signal 7 corresponds to a resolution of the screen unit 4. Inthis context, the second detector unit 24 calculates from at least twovalues of the digitised signal 7 transformed into the frequency domaineither the mean value or the mean squared value or the maximum value orthe minimum value or the auto-peak value. If the screen unit 4 providesa resolution in the horizontal axis of, for example, 1000 pixels, andthe matrix 23, which contains the spectrogram of the digitised signal 7,provides, for example, 10,000 columns with measured values, the seconddetector unit 24 combines ten measured values respectively, using thenamed decimation methods, to form one, new decimated measured value. Thesame also applies for the vertical axis of the screen unit 4. If thevertical axis of the screen unit 4 also provides, for example, 1000pixels, and the matrix 23 also comprises 10,000 row entries withmeasured values, the second detector unit 24 calculates one new,decimated measured value from the measured values from ten rows in eachcase.

The second detector unit 24 is also used to calculate the characteristicof the spectrum for the digitised signal 7 transformed into thefrequency domain and to transfer this to the screen unit 4. In order toobtain a characteristic of the spectrum for the digitised signal 7transformed into the frequency domain, the second detector unit 24decimates the spectrogram in such a manner that only a given number ofrows, which can be selected, are decimated by means of the decimationmethods described. This factual situation will be discussed in greaterdetail below.

FIG. 3 shows an exemplary embodiment which describes in greater detailthe method of functioning of the arrangement 1 according to theinvention for signal analysis after the loading of a signal 7 to beanalysed. FIG. 3 shows one possibility for how the spectrogram 30 of thedigitised signal 7, the characteristic of the spectrum 31 of thedigitised signal 7 and the characteristic of the digitised signal 7present in the time domain can be displayed together and at the sametime on the screen unit 4. Accordingly, FIG. 3 shows three diagrams 33,34, 35, into which the signal 7 to be analysed is plotted in differentways.

The spectrogram 30 of the decimated, digitised signal 7 transformed intothe frequency domain is plotted in a first diagram 33. The frequency isplotted on the horizontal axis of the first diagram 33, increasing inthe direction towards the right. The time t, which increases downwards,is plotted on the vertical axis of the first diagram 33. The amplitude,or respectively the energy of the individual signal components at agiven frequency and at a given time is illustrated by hatching. Thedarker the hatching is the higher the amplitude or respectively thesignal energy. By preference, this information would be displayed on ascreen unit 4 by a different choice of colour. The lighter the colourtone, the higher the signal energy would be. It is also evident from thefirst diagram 33 that there are seven signal impulses 37 ₁, 37 ₂, 37 ₃,37 ₄, 37 ₅, 37 ₆ and 37 ₇, which are broadcast with a time interval fromone another, whereas three 37 ₃, 37 ₄, 37 ₅ of these signal impulses 37₁ to 37 ₇ are transmitted on a first frequency, two 37 ₁, 37 ₂ of thesesignal impulses 37 ₁ to 37 ₇ are transmitted on a second frequency, andtwo 37 ₆, 37 ₇ of these signal impulses 37 ₁ to 37 ₇ are transmitted ona third frequency. The signal energy of the signal impulses 37 ₁, 37 ₂,is highest, followed by the signal impulses 37 ₃, 37 ₄, 37 ₄ and thesignal impulses 37 ₆, 37 ₇.

This digitised signal 7 illustrated in the first diagram 33 is amulti-band GSM signal with different frames (German: Rahmen) in whichdifferent slots (German: Schlitze) are active.

A selection range 36 is also plotted in the first diagram 33. Thisselection range 36 can be adapted arbitrarily in its size (frequency andtime), as will be explained below. The digitised signal 7, of which thespectrum 30 over time is illustrated in the first diagram 33 in FIG. 3,as already described, provides a total of seven signal impulses 37 ₁, 37₂, 37 ₃, 37 ₄, 37 ₅, 37 ₆ and 37 ₇, of which the signal energy, and timeand frequency at which they occur, differ from one another in somecases. It is evident that part of the signal impulses 37 ₂ and 37 ₇ isdisposed within the selection range 36.

Moreover, further, narrow-band interference spurs, which are shown by adifferent hatching and, accordingly, different signal energy, arepresent in the first diagram 33.

The characteristic of the spectrum 31 of the digitised signal 7 isdisplayed in the second diagram 34 from FIG. 3. As in the case of thespectrogram 30 from the first diagram 33, the frequency f is alsoplotted on the horizontal axis. The amplitude A, or respectively thesignal energy, is plotted on the vertical axis of the second diagram 34.It is evident that signal amplitudes of different heights are present inthe characteristic of the spectrum 31 of the digitised signal 7.Accordingly, two signal peaks are identifiable in the second diagram 34.The first signal peak corresponds to the signal impulse 37 ₂, and thesecond signal peak corresponds to the signal impulse 37 ₇. The signalimpulses 37 ₂, 37 ₇ illustrated in the second diagram 34 are the signalimpulses 37 ₂, 37 ₇, which are disposed partially within the selectionrange 36 in the first diagram 33.

The second detector unit 24 decimates the amplitude values over theselected time range within the selection range 36 according to anadjustable or pre-set decimation mode and displays these decimatedvalues in the second diagram 34. If the selection range 36 from thefirst diagram 33 were to be displaced slightly downwards, the signalimpulse 37 ₂ would no longer be displayed in the second diagram 34,whereas, by contrast, the signal impulse 37 ₇ would increase in itsamplitude dependent upon the decimation mode adjusted. This applies inparticular for the mean-value and mean-squared-value decimation modes.

The time characteristic 32 of the digitised signal 7 is displayed in thethird diagram 35 from FIG. 3. The time t is plotted on the horizontalaxis, whereas the amplitude A, or respectively the signal energy, isplotted on the vertical axis. Seven signal impulses 37 ₁, 37 ₂, 37 ₃, 37₄, 37 ₅, 37 ₆ and 37 ₇, which correspond to the signal impulses 37 ₁, 37₂, 37 ₃, 37 ₄, 37 ₅, 37 ₆ and 37 ₇ from the first diagram 33 are shown.The pass range of the bandpass filter 20 from FIG. 2 is adjusted in sucha manner that it corresponds to the frequency range selected by theselection range 36 in the first diagram 33. Undesired interference spurscan be filtered out from the third diagram 35 by varying the position orthe size of the selection range 36.

FIG. 4 shows a further exemplary embodiment which describes in greaterdetail the method of functioning of the arrangement 1 for signalanalysis after loading a signal 7 to be analysed. Once again, the threediagrams 33, 34, 35 are shown illustrated on the screen unit 4. Theseven signal impulses 37 ₁ to 37 ₇ are also illustrated in the firstdiagram 33. By contrast, the selection range 36 is adjusted in such amanner that it covers approximately the same area in its time range andfrequency range as the signal impulse 37 ₂. The selection range 36 canbe adjusted, on the one hand, via the input unit 5 and, on the otherhand, via an automatic recognition of the signal amplitude by the atleast one central data-processing unit 2, whereas this is compared witha previously specified threshold value.

The second diagram 34 from FIG. 4 shows the characteristic of thespectrum 31 of the digitised signal 7. In this context, the signalimpulse 37 ₂ which is disposed at the same position as the signalimpulse 37 ₂ in the first diagram 33, is evident in the second diagram34. Two vertical limit lines 38 ₁, 38 ₂, of which the mutual spacingdistance includes the same frequency range 39 as the selection range 36from the first diagram 33, have also been plotted in the second diagram34.

The time characteristic 32 of the digitised signal 7 is displayed in thethird diagram 35. Accordingly, the pass range of the bandpass filter 20from FIG. 2 is adjusted in such a manner that it is approximately aswide as the frequency range 39. The two signal impulses 37 ₁ and 37 ₂are also shown. Two vertical limit lines 40 ₁, 40 ₂, of which the mutualspacing corresponds to the time range 41, as also specified by theselection range 36 in the first diagram 33, are also displayed.

As soon as the size of the selection range 36 from the first diagram 33is varied, the vertical limit lines 38 ₁, 38 ₂ and 40 ₁, 40 ₂ areautomatically adapted by the at least one central data-processing unitwith regard to their mutual spacing distance. In this context, thecharacteristic of the spectrum 31 and the time characteristic 32 of thedigitised signal 7 are also adapted at the same time.

It is also possible for the vertical limit lines 38 ₁, 38 ₂ and 40 ₁, 40₂ to be varied by the input unit 5 with regard to their mutual spacingand their absolute position in the diagrams 34 and 35. As soon as one ofthe vertical limit lines 38 ₁, 38 ₂ and 40 ₁, 40 ₂ is varied, the atleast one central data-processing unit 2 updates the selection range 36in the first diagram 33.

At the same time, the characteristic of the spectrum 31 and of thedigitised signal 7 present in the time domain is also changed. This isassociated with the fact that the bandpass filter 20 and the firstdetection unit 21 and/or the second detection unit 24 are matched intheir mode of operation by varying one of the vertical limit lines 38 ₁,38 ₂ and 40 ₁, 40 ₂. In this context, it must be specified that the atleast one central data-processing unit 2 controls the screen unit 4 insuch a manner that the spectrogram 30, the characteristic of thespectrum 31 and the characteristic 32 of the digitised signal 7 in thetime domain are displayed together and, above all, simultaneously on thescreen unit 4.

As soon as the selection range 36 frames the signal impulse 37 ₂ in anoptimum manner, the part of the digitised signal 7, which is disposedwithin the selection range 36, can be transferred to an evaluation unit6. The selection unit 6 can also include a modulation analysis. Asillustrated in FIG. 2, however, it is not the decimated, digitisedsignal 7 which is transferred to the evaluation unit 6, but rather thedigitised signal 7 which has not yet been reduced in its resolution.

FIG. 5A shows an exemplary embodiment which describes in greater detailthe method of functioning of the arrangement 1 according to theinvention for signal analysis for the analysis of interference spurs 50within a loaded signal 7. The three diagrams 33, 34, 35, which aredisplayed together on the screen unit 4 and illustrate the digitisedsignal 7 simultaneously in different ways, are also shown. The selectionrange 36, which is moved across the spectrogram 30, is also displayed.In the illustration from FIG. 5A, part of the signal impulse 37 ₆ isdisposed within the selection range 36. In the first diagram, it is alsoevident that a small interference spur 50 is also disposed within theselection range 36. The bandpass filter 20 and the first and seconddetector unit 21, 24 are adapted correspondingly to the selection range36. In the second diagram 34, it is evident that the vertical limitlines 38 ₁, 38 ₂ include within their mutual spacing distance the samefrequency range 39 as the selection range 36. The signal impulse 37 ₆ isstill disposed to a certain extent within the vertical limit lines 38 ₁and 38 ₂. It is also shown very clearly that an interference spur 50(English: spur) occurs within the selection range 36.

In the third diagram 35 from FIG. 5A, the various signal impulses 37 ₁,37 ₂, 37 ₃, 37 ₄, 37 ₅ which are not filtered through the bandpassfilter 20, are also shown. However, the signal impulses 37 ₆, 37 ₇ havebeen filtered out. Similarly, the vertical limit lines 40 ₁, 40 ₂ aredisplayed. In this diagram, the interference spur 50 is not visiblebecause of the wide pass range of the bandpass filter 20. However, thisinterference spur 50 can be displayed in the third diagram 35 byselecting a different decimation mode.

FIG. 5B shows a further exemplary embodiment, which describes in greaterdetail the method of functioning of the arrangement 1 according to theinvention for signal analysis for the analysis of interference spurs 50within a loaded signal 7. In the first diagram 33, it is evident thatthe selection range 36 has been adjusted in such a manner that it framesthe interference spur 50 as accurately as possible. As alreadydescribed, this can be achieved by adjusting the selection range 36 inthe first diagram 33 roughly to the interference spur 50 and then movingthe vertical limit lines 38 ₁, 38 ₂ and 40 ₁, 40 ₂ in the second diagram34 and the third diagram 35 as close as possible to the interferencespur. In this first diagram 33, a further broadband interference spur 51is also shown. However, this will be described separately below.

In the second diagram 34, it is also clearly visible that the verticallimit lines 38 ₁ and 38 ₂ frame the interference spur 50 as accuratelyas possible. In this context, the characteristic of the spectrum 31 isalso still shown within this range with the signal impulse 37 ₆. In thethird diagram 35, the vertical limit lines 40 ₁ and 40 ₂ are alsoadjusted in such a manner that they frame the interference spur 50 asaccurately as possible. The characteristic 32 of the digitised signal 7present in the time domain is also very clearly evident with its twosignal impulses 37 ₁ and 37 ₂.

Moreover, the content of the selection range 36 can be transferred bythe at least one central data-processing unit 2 to the evaluation unit 6in order to draw more accurate conclusions about the type ofinterference spur 50. As already mentioned, the un-decimated, digitisedsignal 7 is transferred to the evaluation unit 6 in this context.

FIG. 6 shows an exemplary embodiment of a flow chart which describes ingreater detail the method of functioning of the arrangement 1 accordingto the invention for signal analysis. As soon as the digitised signal 7is loaded from a signal analyser 8 or an oscilloscope into thearrangement 1 for signal analysis, the first method step S₁ can beimplemented. Within the first method step, the at least one centraldata-processing unit 2 calculates the spectrum 31 and the spectrogram 30of the digitised signal 7. This takes place by means of conventional,known methods. In order to avoid repeating this calculation constantlyin the case of a change of the selection range 36, it is advantageous ifthe at least one central data-processing unit 2 buffers the digitisedsignal 7 transformed into the frequency domain in a buffer unit 3.

Following this, the second method step S₂ is implemented, in which theat least one central data-processing unit 2 controls the screen unit 4in such a manner that the characteristic of the spectrum 31, of thespectrogram 30 and the characteristic 32 of the digitised signal 7present in the time domain are displayed together on the screen unit 4.

Method step S₃ can then be implemented. Within this method step, thespectrogram 30 of the digitised signal 7 is displayed in a first diagram33. The characteristic of the spectrum 31 of the digitised signal 7 isdisplayed in a second diagram 34, and the characteristic 32 of thedigitised signal 7 present in the time domain in a third diagram 35. Thecorresponding signals are displayed by the at least one centraldata-processing unit 2 in the diagrams 33, 34, 35, on the screen unit 4at the same time.

Moreover, method step S₄ can then be implemented. Within method step S₄,a frequency range 39 and a time range 41 can be freely selected withinthe spectrogram 30, whereas, at the same time, the characteristic of thespectrum 31 and the time characteristic 32 of the digitised signal 7 canbe updated by the at least one central data-processing unit 2 dependentupon the selected frequency range 39 and the time range 41, and whereasthe updated characteristics 31, 32 are displayed by the former on thescreen unit 4. It is also possible for the frequency range 39 selectedin the spectrogram 30 to be plotted in the second diagram 34 by the atleast one central data-processing unit 2, and for the time range 41selected in the spectrogram 30 to be plotted by the at least one centraldata-processing unit 2 in the third diagram 35. The free selection ofthe frequency range 39 and the time range 41 also relates to thearbitrary adjustment of the selection range 36 with regard to itsposition and its dimensions within the spectrogram 30.

Method step S₅ can be implemented after method step S₃ or method stepS₄. Within method step S₅, the frequency range 39 in the second diagram34 for the characteristic of the spectrum 31 can be freely selected,whereas the time characteristic of the digitised signal 7 is updated onthe basis of the frequency range 39 selected by the at least one centraldata-processing unit 2 in the third diagram 35, and/or whereas theselected frequency range 39 is plotted in the first diagram 33 for thespectrogram 30 by the at least one central data-processing unit 2, orthe already present selection range 36 is adapted accordingly.

Method step S₆ can be implemented following method step S₃, S₄ or S₅.Within method step S₆, the time range 41 in the third diagram 35 for thetime characteristic 32 of the digitised signal 7 can be freely selected,whereas the at least one central data-processing unit 2 updates thecharacteristic of the spectrum 31 within the second diagram 34 for theselected time range 41, and/or whereas the at least one centraldata-processing unit 2 plots the selected time range 41 into the firstdiagram 33 for the spectrogram 30, or respectively adapts the selectionrange 36 accordingly.

Finally, FIG. 7 shows a further exemplary embodiment of a flow chart,which describes in greater detail the method of functioning of thearrangement 1 according to the invention for signal analysis. In thefurther course, method step S₇ is implemented, which is, however,preferably not necessarily implemented before method step S₂. Withinmethod step S₇, the digitised signal 7 present in the time domain isfiltered through a bandpass filter 20, whereas the pass range of thebandpass filter 20 corresponds to the selected frequency range 39 of thefirst diagram 33 for the spectrogram 30 or to the selected frequencyrange 39 of the second diagram 34 for the characteristic of the spectrum31. Since this bandpass filter 20 is a digital filter, its parameterscan be adapted particularly readily to the current settings of theselection range 36. If no frequency range 39 has been selected, astandard frequency range is set, which is obtained, for example, fromthe bandwidth of the digitised signal 7.

After method step S₇, method step S₈ can be implemented. Method step S₈is also preferably implemented before method step S₂. Within method stepS₈, the filtered, digitised signal 7 can be decimated in its resolutionby a first detector unit 21, so that the decimated, digitised signal 7corresponds to a resolution of the screen unit 4, whereas either themean value or the mean squared value or a maximum value or the minimumvalue or the auto-peak value from at least two values of the digitisedsignal 7 is calculated by the first detector unit 21. Within method stepS₈, it is also possible for the digitised signal 7 transformed into thefrequency domain to be decimated in its resolution by the seconddetector unit 24, so that the decimated, digitised signal 7 correspondsto a resolution of the screen unit 4, whereas either the mean value orthe mean squared value or the maximum value or the minimum value or theauto-peak value is calculated by the second detector unit 24 from atleast two values of the digital signal 7.

Following method step S₇ or method step S₈, method step S₉ can beimplemented. However, method step S₉ is preferably implemented aftermethod step S₄, method step S₅ or method step S₆. In method step S₉, thepart of the digitised signal 7, which is disposed within the selectedtime range 41 and/or within the selected frequency range 39 istransferred by the at least one central data-processing unit 2 to anevaluation unit 6. The part which is disposed within the selection range36, or respectively within the vertical limit lines 38 ₁, 38 ₂ or 40 ₁,40 ₂ and is transferred to the selection unit 6, relates to the part ofthe digitised signal 7, which has not yet been decimated. A given partof the spectrum, the time characteristic 32 of the digitised signal 7 orthe spectrogram 30 can be transferred to the selection unit 6.

The filter, which is realised as the bandpass filter 20, is preferably araised-cosine filter (German: ansteigender Kosinus filter). However,other types of filter can also be used.

Within the scope of the invention, all of the features described and/orillustrated can be combined with one another as required. In particular,the dependent claims, relating to the method, can also be combined withthe device claims relating to the arrangement 1 for signal analysis andvice versa.

The invention claimed is:
 1. An arrangement for signal analysis,comprising: at least one central data-processing unit; and a screen unitconnected to the at least one central data-processing unit, wherein thecentral data-processing unit calculates a spectrum and a spectrogramfrom a digitised signal, wherein the at least one centraldata-processing unit controls the screen unit so that the spectrogram ofthe digitised signal, a representation of the spectrum of the digitisedsignal, and a representation of the digitised signal present in the timedomain can be displayed together on the screen unit, and wherein thespectrogram of the digitised signal is displayed on the screen unit in afirst diagram and the representation of the spectrum of the digitisedsignal is displayed in a second diagram by the at least one centraldata-processing unit at the same time on the screen unit.
 2. Thearrangement for signal analysis according to claim 1, wherein thedigitised signal can be buffered by the at least one centraldata-processing unit in a buffer unit and that the digitised signal istransformed into the frequency domain by the at least one centraldata-processing unit and can be buffered in the buffer unit.
 3. Thearrangement for signal analysis according to claim 1, wherein afrequency range and a time range within the spectrogram can be freelyselected, and wherein the representation of the spectrum or the timerepresentation of the digitised signal can be updated by the at leastone central data-processing unit for the selected frequency range andtime range and displayed on the screen unit, and/or wherein thefrequency range selected in the spectrogram can be plotted in the seconddiagram by the at least one central data-processing unit, or the timerange selected in the spectrogram can be plotted in the second diagramby the at least one central data-processing unit.
 4. The arrangement forsignal analysis according to claim 1, wherein a frequency range withinthe second diagram can be freely selected for the representation of thespectrum in the case that the spectrum of the digitised signal isdisplayed in the second diagram, and/or wherein the frequency rangeselected in the second diagram can be plotted in the first diagram forthe spectrogram by the at least one central data-processing unit.
 5. Thearrangement for signal analysis according to claim 1, wherein in thecase that the representation of the digitised signal in the time domainis displayed in the second diagram, a time range within the seconddiagram can be freely selected for the time representation of thedigitised signal, or wherein the representation of the spectrum can beupdated by the at least one central data-processing unit on the basis ofthe selected time range, and/or wherein the time range selected in thesecond diagram can be plotted in the first diagram for the spectrum bythe at least one central data-processing unit.
 6. The arrangement forsignal analysis according to claim 1, wherein a part of the digitisedsignal which is disposed within a selected time range or frequency rangecan be transferred to an evaluation unit by the at least one centraldata-processing unit.
 7. A method for operating an arrangement forsignal analysis including at least one central data-processing unit anda screen unit connected to the at least one central data-processingunit, comprising: calculating a spectrum and a spectrogram from adigitised signal by the central data-processing unit; displaying thespectrogram of the digitised signal, of a representation of the spectrumof the digitised signal, and of a representation of the digitised signalpresent in the time domain together on the screen unit by the at leastone central data-processing unit; and displaying the spectrogram of thedigitised signal in a first diagram and the representation of thespectrum of the digitised signal in a second diagram at the same time onthe screen unit by the at least one central data-processing unit.
 8. Themethod according to claim 7, further comprising: freely selecting afrequency range and a time range within the spectrogram; and updatingthe representation of the spectrum or of the time representation of thedigitised signal by the at least one central data-processing unit forthe selected frequency range or time range; and displaying the updatedrepresentation on the screen unit; and/or plotting the frequency rangeselected in the spectrogram into the second diagram by the at least onecentral data-processing unit; or plotting the time range selected in thespectrogram into the second diagram by the at least one centraldata-processing unit.
 9. The method according to claim 7, furthercomprising: freely selecting a frequency range within the second diagramfor the representation of the spectrum in the case that the spectrum ofthe digitised signal is displayed in the second diagram; or updating thetime representation of the digitised signal on the basis of the selectedfrequency range by the at least one central data-processing unit; and/orplotting the frequency range selected in the second diagram into thefirst diagram for the spectrogram by the at least one centraldata-processing unit.
 10. The method according to claim 7, furthercomprising: freely selecting a time range within the second diagram forthe time representation of the digitised signal in the case that therepresentation of the digitised signal in the time domain is displayedin the second diagram; and/or plotting the time range selected in thesecond diagram into the first diagram for the spectrogram by the atleast one central data-processing unit.
 11. The method according toclaim 7, further comprising filtering the digitised signal present inthe time domain by a bandpass filter, wherein a pass range of thebandpass filter corresponds to a selected frequency range of the firstdiagram for the spectrogram.
 12. The method according to claim 11,further comprising: decimating the filtered digitised signal in itsresolution by a first detector unit, so that the decimated, digitisedsignal corresponds to a resolution of the screen unit, wherein a valueselected from the group consisting of a mean value, a mean squaredvalue, a maximum value, a minimum value, or an auto-peak value of atleast two values of the digitised signal is calculated by the firstdetector unit; and/or decimating the digitised signal transformed intothe frequency range in its resolution by a second detector unit, so thatthe decimated, digitised signal corresponds to a resolution of thescreen unit, wherein either the mean value or the mean squared value orthe maximum value or the minimum value or the auto-peak value of the atleast two values of the digitised signal is calculated by the seconddetector unit.
 13. The method according to claim 12, further comprisingtransferring a part of the digitised signal which is disposed within theselected time range or frequency range by the at least one centraldata-processing unit to an evaluation unit.
 14. A non-transitorycomputer-readable storage medium storing a computer program, in order toimplement the method according to claim 7 when the computer program isexecuted on a computer or a digital signal processor.
 15. An arrangementfor signal analysis, comprising: at least one central data-processingunit; and a screen unit connected to the at least one centraldata-processing unit, wherein the central data-processing unitcalculates a spectrum and a spectrogram from a digitised signal, whereinthe at least one central data-processing unit controls the screen unitso that the spectrogram of the digitised signal, a representation of thespectrum of the digitised signal, and a representation of the digitisedsignal in the time domain can be displayed together on the screen unit,and wherein the spectrogram of the digitised signal is displayed on thescreen unit in a first diagram and the representation of the digitisedsignal in the time domain is displayed in a second diagram by the atleast one central data-processing unit at the same time on the screenunit.
 16. The arrangement for signal analysis according to claim 15,wherein the digitised signal present in the time range can be filteredby a bandpass filter, and wherein a pass range of the bandpass filtercorresponds to a selected frequency range of the first diagram for thespectrogram.
 17. The arrangement for signal analysis according to claim16, wherein the filtered, digitised signal can be decimated in itsresolution by a first detector unit, so that the decimated, digitisedsignal corresponds to a resolution of the screen unit, wherein a valueselected from the group consisting of a mean value, a mean squaredvalue, a maximum value, a minimum value, or an auto-peak value of atleast two values of the digitised signal can be calculated by the firstdetector unit, and/or wherein the digitised signal transformed into thefrequency domain can be decimated in its resolution by a second detectorunit, so that the decimated, digitised signal corresponds to aresolution of the screen unit, wherein the mean value or the meansquared value or the maximum value or the minimum value or the auto-peakvalue of the at least two values of the digitised signal can becalculated by the second detector unit.
 18. The arrangement for signalanalysis according to claim 15, wherein the digitised signal can bebuffered by the at least one central data-processing unit in a bufferunit and that the digitised signal is transformed into the frequencydomain by the at least one central data-processing unit and can bebuffered in the buffer unit.
 19. The arrangement for signal analysisaccording to claim 15, wherein a frequency range and a time range withinthe spectrogram can be freely selected, and wherein the representationof the spectrum or the time representation of the digitised signal canbe updated by the at least one central data-processing unit for theselected frequency range and time range and displayed on the screenunit, and/or wherein the frequency range selected in the spectrogram canbe plotted in the second diagram by the at least one centraldata-processing unit, or the time range selected in the spectrogram canbe plotted in the second diagram by the at least one centraldata-processing unit.
 20. The arrangement for signal analysis accordingto claim 15, wherein a frequency range within the second diagram can befreely selected for the representation of the spectrum in the case thatthe spectrum of the digitised signal is displayed in the second diagram,and/or wherein the frequency range selected in the second diagram can beplotted in the first diagram for the spectrogram by the at least onecentral data-processing unit.
 21. The arrangement for signal analysisaccording to claim 15, wherein in the case that the representation ofthe digitised signal in the time domain is displayed in the seconddiagram, a time range within the second diagram can be freely selectedfor the time representation of the digitised signal, or wherein therepresentation of the spectrum can be updated by the at least onecentral data-processing unit on the basis of the selected time range,and/or wherein the time range selected in the second diagram can beplotted in the first diagram for the spectrum by the at least onecentral data-processing unit.
 22. The arrangement for signal analysisaccording to claim 15, wherein a part of the digitised signal which isdisposed within a selected time range or frequency range can betransferred to an evaluation unit by the at least one centraldata-processing unit.
 23. A method for operating an arrangement forsignal analysis including at least one central data-processing unit anda screen unit connected to the at least one central data-processingunit, comprising: calculating a spectrum and a spectrogram from adigitised signal by the central data-processing unit; displaying thespectrogram of the digitised signal of a representation of the spectrumof the digitised signal and of a representation of the digitised signalin the time domain together on the screen unit by the at least onecentral data-processing unit; and displaying the spectrogram of thedigitised signal in a first diagram and the representation of thedigitised signal in the time domain in a second diagram at the same timeon the screen unit by the at least one central data-processing unit. 24.The method according to claim 23, further comprising: freely selecting afrequency range and a time range within the spectrogram; and updatingthe representation of the spectrum or of the time representation of thedigitised signal by the at least one central data-processing unit forthe selected frequency range or time range; and displaying the updatedrepresentation on the screen unit; and/or plotting the frequency rangeselected in the spectrogram into the second diagram by the at least onecentral data-processing unit; or plotting the time range selected in thespectrogram into the second diagram by the at least one centraldata-processing unit.
 25. The method according to claim 23, furthercomprising: freely selecting a frequency range within the second diagramfor the representation of the spectrum in the case that the spectrum ofthe digitised signal is displayed in the second diagram; or updating thetime representation of the digitised signal on the basis of the selectedfrequency range by the at least one central data-processing unit; and/orplotting the frequency range selected in the second diagram into thefirst diagram for the spectrogram by the at least one centraldata-processing unit.
 26. The method according to claim 23, furthercomprising: freely selecting a time range within the second diagram forthe time representation of the digitised signal in the case that therepresentation of the digitised signal in the time domain is displayedin the second diagram; and/or plotting the time range selected in thesecond diagram into the first diagram for the spectrogram by the atleast one central data-processing unit.
 27. A non-transitorycomputer-readable storage medium storing a computer program, in order toimplement the method according to claim 23 when the computer program isexecuted on a computer or a digital signal processor.